Fahrenheit (°F) - Unit Information & Conversion

Quick Answer

What is Fahrenheit? Fahrenheit (°F) is a temperature scale where water freezes at 32°F and boils at 212°F at sea level. It's the standard temperature measurement in the United States for weather, cooking, and daily life. Room temperature is about 68-72°F, and normal body temperature is 98.6°F. Use our temperature converter to convert Fahrenheit to Celsius, Kelvin, and more instantly.

Quick Comparison Table

Fahrenheit	Celsius	Description	Convert Now
-40°F	-40°C	Extremely cold (same in both scales)	Convert →
0°F	-17.8°C	Very cold winter day	Convert →
32°F	0°C	Water freezes	Convert →
50°F	10°C	Cool spring day	Convert →
68°F	20°C	Room temperature	Convert →
98.6°F	37°C	Normal body temperature	Convert →
212°F	100°C	Water boils	Convert →

Need a different conversion? Try our temperature converter for all temperature units.

Definition

Degree Fahrenheit (symbol: °F) is a unit of temperature on the Fahrenheit scale, developed by physicist Daniel Gabriel Fahrenheit in 1724. It is one of the most commonly used temperature scales in the United States.

Key reference points:

• Water freezing point: 32°F (at standard atmospheric pressure)
• Water boiling point: 212°F (at standard atmospheric pressure)
• Degree span: 180°F between freezing and boiling (212 - 32 = 180)
• Absolute zero: -459.67°F (theoretical lowest temperature)

Conversion formulas:

• To Celsius: °C = (°F - 32) × 5/9 - Convert F to C
• To Kelvin: K = (°F - 32) × 5/9 + 273.15 - Convert F to K
• From Celsius: °F = (°C × 9/5) + 32 - Convert C to F

Common temperature ranges:

• Below 0°F: Extremely cold
• 0-32°F: Very cold (below freezing)
• 32-50°F: Cold
• 50-65°F: Cool
• 65-75°F: Comfortable/room temperature
• 75-85°F: Warm
• 85-95°F: Hot
• Above 95°F: Very hot

Note: The degree symbol (°) is always used with Fahrenheit. Write "32°F" not "32F" or "32 degrees F."

Convert between temperature units: Fahrenheit converter

History

• Daniel Gabriel Fahrenheit (1686-1736): A Polish-German physicist and instrument maker who invented the mercury thermometer and developed the Fahrenheit temperature scale.

• Early Development (1724): Fahrenheit proposed his temperature scale with three reference points:

  • 0°F: Temperature of a brine solution (mixture of ice, water, and ammonium chloride salt) - the coldest temperature he could reliably reproduce in his laboratory
  • 32°F: Freezing point of water (later standardized)
  • 96°F: Human body temperature (later adjusted to 98.6°F)

• Original Rationale: Fahrenheit chose these points to:

  • Avoid negative numbers in normal weather (unlike earlier scales)
  • Create finer graduations for better precision (180 degrees between freezing and boiling vs 100 in Celsius)
  • Use easily reproducible reference points with 18th-century technology

• Refinements (1750s onward): The scale was gradually standardized:

  • Water's freezing point: exactly 32°F
  • Water's boiling point: exactly 212°F (at standard atmospheric pressure)
  • This created 180 degrees between the two points
  • Human body temperature was remeasured at 98.6°F (not 96°F)

• Rapid Adoption (1700s-1800s): The Fahrenheit scale quickly became popular:

  • Adopted throughout the British Empire
  • Standard in English-speaking countries
  • Used in scientific work until the late 19th century
  • Mercury thermometers using Fahrenheit became widespread

• Celsius Competition (1742): Anders Celsius proposed the centigrade scale (later renamed Celsius) with 0° at water freezing and 100° at boiling. Simpler, but both scales coexisted.

• Metric Movement (1900s): As the metric system spread globally:

  • Most countries switched from Fahrenheit to Celsius
  • Scientific community adopted Celsius/Kelvin
  • UK officially switched to Celsius in the 1960s-1970s
  • Canada switched to Celsius in the 1970s

• United States Today: The US remains the only major country using Fahrenheit for everyday temperatures:

  • Weather forecasts in °F
  • Thermostats and home heating/cooling in °F
  • Cooking temperatures in °F
  • Medical thermometers in °F (though hospitals also use Celsius)
  • Scientific and medical research uses Celsius/Kelvin

• Why the US Kept Fahrenheit:

  • Deeply ingrained in culture and infrastructure
  • Costly to replace all thermostats, ovens, signs
  • Public resistance to metric conversion
  • Fahrenheit provides finer resolution for weather (1°F = 0.56°C)

• Global Usage Today:

  • Primary users: United States, some Caribbean nations (Bahamas, Belize, Cayman Islands), Palau, Federated States of Micronesia, Marshall Islands
  • Former users: UK, Canada, Australia (all switched to Celsius)
  • Rest of world: Uses Celsius exclusively

• Cultural Impact: Fahrenheit remains a distinctive American characteristic, like miles and pounds, symbolizing resistance to metric adoption.

Real-World Examples

Weather and Climate

Extreme Temperatures:

• Hottest recorded on Earth: 134°F (56.7°C) - Death Valley, California, 1913
• Coldest recorded on Earth: -128.6°F (-89.2°C) - Vostok Station, Antarctica, 1983
• Hottest US city average: Phoenix, AZ - Summer highs 105-110°F
• Coldest US city average: Fairbanks, AK - Winter lows -10 to -20°F

Seasonal Temperatures (US typical):

• Winter: 20-40°F (most of US), colder in North
• Spring: 50-70°F
• Summer: 75-95°F (varies widely by region)
• Fall: 50-70°F

Regional Variations:

• Florida summer: 85-95°F with high humidity
• Arizona summer: 100-115°F dry heat
• Minnesota winter: -10 to 20°F
• San Francisco year-round: 50-70°F (mild)
• Hawaii year-round: 75-85°F (tropical)

Weather Descriptions:

• Below 0°F: Dangerously cold, frostbite risk
• 0-20°F: Extremely cold, winter gear essential
• 20-32°F: Very cold, below freezing
• 32-50°F: Cold, jacket weather
• 50-65°F: Cool, light jacket
• 65-75°F: Pleasant, comfortable
• 75-85°F: Warm, shorts weather
• 85-95°F: Hot, air conditioning recommended
• 95-105°F: Very hot, heat advisory
• Above 105°F: Dangerously hot, stay indoors

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Human Body Temperature

Normal and Abnormal:

• Normal body temp: 98.6°F (37°C) average, range 97-99°F
• Low-grade fever: 99-100.4°F
• Fever: 100.4-102°F
• High fever: 102-104°F
• Dangerous fever: Above 104°F (seek medical attention)
• Hypothermia: Below 95°F
• Severe hypothermia: Below 90°F (life-threatening)

Infant/Child Temperature:

• Normal (oral): 97.5-99.5°F
• Fever threshold: Above 100.4°F (38°C)
• High fever: Above 102°F (call doctor)

Measurement Methods:

• Oral: Standard adult method, 98.6°F average
• Rectal: 0.5-1°F higher than oral (most accurate)
• Armpit: 0.5-1°F lower than oral (least accurate)
• Ear (tympanic): Similar to oral when done correctly
• Forehead: Convenient but less accurate

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Cooking and Baking

Oven Temperatures:

• Warm: 200°F - Keeping food warm
• Low: 250-300°F - Slow roasting, dehydrating
• Moderate: 325-350°F - Most baking (cookies, cakes)
• Medium-high: 375-400°F - Roasting vegetables, chicken
• High: 425-450°F - Pizza, roasted meats
• Very high: 475-500°F - Pizza stone, searing
• Broil: 500-550°F - Top browning

Common Baking Temps:

• Cookies: 350-375°F
• Cakes: 325-350°F
• Bread: 350-450°F (varies by type)
• Muffins: 375-400°F
• Pie crust: 375-425°F
• Pizza: 450-500°F
• Roast turkey: 325-350°F
• Roast chicken: 375-425°F

Meat Internal Temperatures (Food Safety):

• Poultry (chicken, turkey): 165°F minimum
• Ground meat (beef, pork): 160°F minimum
• Beef steaks/roasts: 145°F (medium-rare) to 160°F (medium-well)
• Pork: 145°F minimum
• Fish: 145°F
• Eggs: 160°F (for dishes containing eggs)

Candy Making:

• Soft ball: 234-240°F (fudge, fondant)
• Hard ball: 250-265°F (caramels, nougat)
• Soft crack: 270-290°F (taffy)
• Hard crack: 300-310°F (brittles, lollipops)
• Caramel: 320-350°F (caramelized sugar)

Oil Frying Temperatures:

• Deep frying: 350-375°F (most foods)
• French fries: 325°F (first fry), 375°F (second fry)
• Chicken: 350-365°F
• Donuts: 365-375°F
• Fish: 350-375°F

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Household and Comfort

Thermostat Settings:

• Winter heating: 68-72°F daytime, 65-68°F nighttime
• Summer cooling: 72-78°F (DOE recommends 78°F when home)
• Energy saving: Lower to 60-65°F when away in winter
• Vacation mode: 55-60°F winter (prevent pipes freezing)

Water Temperatures:

• Hot water heater: 120°F (recommended for safety and efficiency)
• Bath water: 100-105°F (comfortable bathing)
• Shower: 105-110°F (typical preference)
• Hot tub/spa: 100-104°F (maximum 104°F for safety)
• Pool water: 78-82°F (comfortable swimming)
• Cold tap water: 50-60°F (varies by location)

Storage Temperatures:

• Refrigerator: 35-38°F (ideal 37°F)
• Freezer: 0°F or below
• Wine storage: 45-65°F (varies by wine type)
• Root cellar: 32-40°F
• Pantry: 50-70°F

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Industrial and Scientific

Material Properties:

• Lead melts: 621°F (327°C)
• Aluminum melts: 1,221°F (660°C)
• Steel melts: 2,500-2,800°F (1,370-1,540°C)
• Glass softens: 1,000-1,500°F
• Wood ignites: 300-500°F (varies by wood type)
• Paper ignites: 451°F (famous from Ray Bradbury's novel)

HVAC and Building:

• Comfortable indoor: 68-76°F
• OSHA workplace: 68-76°F recommended
• Humidity with temp: 30-50% relative humidity ideal at 68-72°F

Engine Temperatures:

• Car engine operating: 195-220°F
• Overheating threshold: Above 230°F
• Engine oil: 195-220°F normal operating
• Transmission fluid: 175-200°F optimal

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Nature and Environment

Plant Growth:

• Frost damage: Below 32°F
• Seedling germination: 60-75°F (most vegetables)
• Tomato growth: 70-85°F optimal
• Grass growth: 60-75°F
• Tropical plants: Above 60°F minimum

Snow and Ice:

• Snow formation: Below 32°F
• Sleet: 32-34°F (freezing rain)
• Black ice forms: 32°F or just below
• Packed snow: 15-32°F
• Powder snow: Below 15°F

Wildlife:

• Bees inactive: Below 50°F
• Mosquitoes inactive: Below 50°F
• Fish active (bass): 65-75°F
• Bird migration triggers: Temperature changes below 50°F

Common Uses

Fahrenheit is the standard temperature scale for daily life in the United States:

Weather Reporting

Primary temperature scale for weather forecasts and reporting in the United States and its territories.

Weather applications:

• Daily temperature forecasts (high/low)
• Current temperature readings
• Heat index calculations
• Wind chill factor
• Severe weather alerts (heat advisories, freeze warnings)
• Historical climate data
• Weather maps and graphics

Why Fahrenheit in weather:

• Finer resolution (1°F increments vs 1°C)
• Human comfort range (0-100°F covers most livable temps)
• Cultural familiarity in the US
• All infrastructure uses Fahrenheit

Convert for international weather: Fahrenheit to Celsius

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Home Heating and Cooling

Standard for thermostats, HVAC systems, and climate control in American homes and buildings.

HVAC uses:

• Thermostat settings (heat/cool)
• Programmable temperature schedules
• Smart home temperature control
• Zone heating/cooling
• Energy efficiency monitoring
• Comfort optimization

Typical settings:

• Winter: 68-70°F daytime, 65°F night
• Summer: 75-78°F when home, 82-85°F when away
• Energy saving: Adjust 7-10°F from comfort level when absent

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Cooking and Food Preparation

Universal standard for oven temperatures, cooking instructions, and food safety in American kitchens.

Cooking applications:

• Oven temperature settings
• Recipe instructions
• Meat thermometer readings
• Food safety guidelines
• Candy/deep-fry thermometers
• Sous vide cooking

Why Fahrenheit in cooking:

• All US recipes use °F
• All ovens manufactured for US in °F
• Food safety standards in °F
• Cookbooks and packaging use °F

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Medical Temperature

Standard for body temperature measurement in US healthcare and home use.

Medical uses:

• Fever detection and monitoring
• Patient vital signs
• Hypothermia/hyperthermia diagnosis
• Pediatric care (baby temperature)
• Home health monitoring
• Medical charts and records

Key thresholds:

• Normal: 98.6°F (97-99°F range)
• Fever: Above 100.4°F
• High fever: Above 103°F
• Hypothermia: Below 95°F

Note: US hospitals often use both Fahrenheit and Celsius for international standardization.

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Swimming Pools and Spas

Standard for pool heating, hot tubs, and aquatic facilities in the US.

Pool/spa uses:

• Pool heater settings
• Spa/hot tub temperature
• Chemical effectiveness (temperature-dependent)
• Comfort optimization
• Energy cost management

Standard temperatures:

• Swimming pool: 78-82°F
• Competitive swimming: 77-82°F
• Hot tub: 100-104°F (max 104°F)
• Therapy pool: 92-98°F

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Automotive

Used for engine monitoring and climate control in US vehicles.

Automotive uses:

• Engine temperature gauge
• Coolant temperature warning
• Cabin climate control
• Outside temperature display
• Oil temperature monitoring

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Everyday Decisions

Influences daily choices in clothing, activities, and comfort throughout the US.

Daily decisions based on temperature:

• What to wear (shorts vs jacket)
• Indoor/outdoor activities
• Exercise safety
• Pet care (walk dog or not)
• Home comfort adjustments

Use our Fahrenheit converter for everyday conversions.

Common Conversion Mistakes to Avoid

❌ Mistake #1: Using °C formula for °F

• Wrong: Thinking 30°F = 30°C
• Correct: 30°F = -1.1°C (very different!)
• Why it matters: 30°C = 86°F (hot vs cold)
• Fix: Always use formula: °C = (°F - 32) × 5/9
• Tool: Fahrenheit to Celsius converter

❌ Mistake #2: Forgetting to subtract 32 first

• Wrong: °C = °F × 5/9 (missing the -32 step)
• Correct: °C = (°F - 32) × 5/9
• Example: 100°F = (100-32) × 5/9 = 37.8°C, NOT 55.6°C
• Order matters: Subtract 32 BEFORE multiplying by 5/9

❌ Mistake #3: Confusing freezing points

• Wrong: Water freezes at 0°F
• Correct: Water freezes at 32°F (0°C)
• Remember: 32°F = 0°C (freezing), 212°F = 100°C (boiling)
• Mnemonic: "Thirty-two freeze" (rhymes)

❌ Mistake #4: Inverted conversion formula

• Wrong: Using F to C formula when converting C to F
• Correct F→C: °C = (°F - 32) × 5/9
• Correct C→F: °F = (°C × 9/5) + 32
• Example: 20°C = (20 × 9/5) + 32 = 68°F

❌ Mistake #5: Rounding too early

• Wrong: (68 - 32) = 36, then 36 × 5 = 180, then 180 ÷ 9 ≈ 20°C
• Better: (68 - 32) × 5/9 = 36 × 0.5556 = 20°C
• Why: Early rounding compounds errors
• Tip: Use calculator or converter for accuracy

❌ Mistake #6: Negative temperature confusion

• Wrong: -40°F = positive Celsius
• Correct: -40°F = -40°C (only point where scales match!)
• Example: -10°F = (-10 - 32) × 5/9 = -23.3°C
• Remember: Below freezing (32°F) always gives negative °C